1. Field of the Invention
This invention relates to a scanning microscope. This invention particularly relates to a scanning microscope provided with an improved mechanism for scanning a sample with a light beam. This invention also relates to a novel scanning mechanism for use in a scanning microscope.
2. Description of the Prior Art
Optical type scanning microscopes have heretofore been used. With the scanning microscope, a laser beam, which serves as a light beam, is converged by an objective lens to a small light spot on a sample, and the sample is scanned with the light spot in a main scanning direction and a sub-scanning direction. The light beam, which has passed through the sample during the scanning, or the light beam, which has been reflected from the sample during the scanning, is detected by a photodetector. An enlarged image of the sample is thereby obtained. Examples of the scanning microscopes are disclosed in Japanese Unexamined Patent Publication Nos. 62(1987)-209510 and 63(1988)-306414.
The conventional scanning microscope utilizes one of the following scanning mechanisms:
(1) a mechanism which two-dimensionally moves the sample supporting member, and
(2) a mechanism which two-dimensionally deflects the laser beam by a light deflector.
However, the scanning mechanism described in (1) has the problem in that the sample flies out of its correct position when it is scanned quickly.
With the scanning mechanism described in (2), the aforesaid problem does not occur, and therefore quick scanning can be achieved. For example, with a scanning mechanism wherein an acousto-optic deflector (AOD) is utilized, the scanning can be carried out with a frequency of as high as 15.75 kHz. In such cases, the period, with which the main scanning is carried out, is equal to 1/(15.75.times.10.sup.3) second. Therefore, for example, when the number of the main scanning lines is 500, the time required for a single image to be formed is as short as approximately 1/30 second. Accordingly, a single image can be formed nearly in the real time mode.
However, in cases where an image signal representing a two-dimensional image of a sample is generated each time the focusing plane is moved, and a three-dimensional image is reconstructed from the image signals thus obtained from a plurality of focusing planes, it is necessary that several tens to several hundreds of two dimensional images of the sample be formed. In such cases, if the imaging speed is on the order described above, it will take several seconds to several tens of seconds for all of the necessary two-dimensional images of the sample to be formed.